stderr log file

[nbari]

Be available to specify a file only for writing logs related only to stderr, probably something like this:

    log:
        file: /var/log/app/access.log
        age: 86400
        num: 3
        size: 1
    stderr:
        file: /var/log/app/error.log
        age: 86400
        num: 3
        size: 1

The complexity of this is the creation of another pair of pipes only for the stderr and another logger that both file/err should be rotated on the defined period

[nbari]

Create 3 log options, keep it simple by just adding an option to write stderr and not merging it into the default log

If log, stdout & stderr will be combined. (default and used also for a custom logger)

log:
  file: /var/log/app/access.log
  age: 86400
  num: 3
  size: 1

if stderr_log stderr, the log file will contain only standard output and the standard error will be written to the defined file.

log:
  file: /var/log/app/access.log
  age: 86400
  num: 3
  size: 1
stderr:
  file: /var/log/app/error.log
  age: 86400
  num: 3
  size: 1

If only stderr there will be no stdout:

stderr:
  file: /var/log/app/error.log
  age: 86400
  num: 3
  size: 1

[nbari]

implemented on 0.16.0